Heat the oil in a large frying pan, and add the chopped vegetables. Cook for a few minutes over a medium heat, until fairly soft. Add the black beans, refried beans and spices, and season to taste. Depending on the kind of refried beans you used, you may want to add additional spices or seasonings at this point (the beans I used were already fairly spicy). Mix thoroughly - you may need to add a dash of water if the mixture seems too thick. You could also add a tin of tomatoes if you prefer a saucier lasagne.

Melt the butter in a small saucepan, and add the flour. Mix well, and cook over a low heat for 1-2 minutes. Add the milk a little at a time, stirring the mixture until smooth each time before adding more. When you have added all of the milk and you have a smooth sauce, add the grated cheese and plenty of salt and pepper. Cook for another minute or two, to melt the cheese.

To assemble the lasagne, start by adding about 1tbsp of cheese sauce to the base of your baking dish, and spread it around - this helps to prevent the lasagne from sticking. From this point onwards, it doesn’t really matter what order you layer up your sauce, beans and pasta. I layered up pasta, then beans, then sauce, until all the ingredients were used. I finished the lasagne with the last of the cheese sauce, and sprinkled some extra grated cheese on top.